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Download page 2025 Los Angeles Wildfire H&H Modeling Workshop, Los Angeles County Public Works, Los Angeles, CA.
2025 Los Angeles Wildfire H&H Modeling Workshop, Los Angeles County Public Works, Los Angeles, CA
Workshop Objectives:
The U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC) has added debris yield and flow capabilities to its popular hydrologic and hydraulic software. HEC’s Hydrologic Modeling System (HEC-HMS) can now compute debris yield/flow and the River Analysis System (HEC-RAS) can simulate the non-Newtonian fluid physics of mud and debris flows associated with post-wildfire events and mine-tailing dam breaches. A three-day workshop is being offered that covers hands on application of debris simulation capabilities in both HEC-HMS and HEC-RAS.
- Understand how HEC-HMS and HEC-RAS address post-wildfire hydrology and debris-flow analysis.
- Gain hands-on experience developing comprehensive post-wildfire hydrologic and hydraulic models, including parameter estimation, calibration, and HEC-HMS implementation.
It is recommended that you use this specific version of HEC-HMS for this workshop and HEC-DSSVue version 3.4.15 for the class. You do not need administrative privileges to install HEC-HMS and HEC-DSSVue. Download HEC-HMS special potable testing version 4.14 alpha (HEC-HMS-4.14-alpha-win-x64_HMS-4430.zip) only for this workshop. Download HEC-DSSVue version 3.4.15 from this page, https://www.hec.usace.army.mil/software/hec-dssvue/downloads.aspx. Then use 7-zip and unzip the files to the C:\Programs directory on your computer (you should have a folder named HEC-HMS-4.13-beta within the C:\Programs directory). Then you can pin HEC-HMS.exe and HEC-DSSVue.exe to your taskbar and open these programs by clicking on the icons.
Workshop Details
- Time: 9-11 September 2025, 0800-1700
- Location: Los Angeles County Public Works (Conference Room E), Los Angeles, CA. 900 S. Fremont Ave. Alhambra, CA 91803
- Instructor:
- Jose Paredez, P.E., Lead Civil Engineer, Hydrology Section, USACE Los Angeles District (SPL) (Workshop Facilitator)
- Jay Pak, Ph.D., P.E., Sr. Research Hydraulic Engineer, US Army Corps of Engineers, Hydrologic Engineering Center (HEC)
- Moosub Eom, Ph.D., P.E., Regional Technical Specialist, Hydraulic Section, USACE Los Angeles District (SPL)
- Nicholas Olsen, Civil Engineer, Hydraulic Section, USACE Los Angeles District (SPL)
- Jackie Oehler, P.E., Civil Engineer, Hydrology Section, USACE Los Angeles District (SPL)
- Instructor Short Biography:
Mr. Jose Paredez is the Lead Civil Engineer in the Hydrology a GIS Section of the Los Angeles District, USACE. A registered Professional Engineer (PE) in California, he brings over 10 years of experience specializing in surface water hydrology and flood risk reduction. Mr. Paredez leads technical efforts on a diverse range of projects, from small urban catchment studies to comprehensive watershed-level rainfall-runoff modeling, including pre- and post-fire hydrology for debris flow simulation. He holds a B.S. from Cal Poly Pomona and an M.S. in Civil Engineering from Kansas State University.
Dr. Jang (Jay) Pak boasts over two decades of experience with the US Army Corps of Engineers (USACE), currently serving as a Senior Research Hydraulic Engineer at the Hydrology & Statistics Division of the Hydrologic Engineering Center (HEC). His expertise encompasses surface water hydrology, post-fire hydrology, river hydraulics, debris flow analysis, land surface erosion, and more. Dr. Pak earned his Ph.D. and Master’s degrees in Civil and Environmental Engineering from the University of Southern California, focusing his doctoral research on real-time debris prediction models integrating wildfire and subsequent storm events. He is a registered civil engineer in the state of California.
Dr. Moosub Eom is a Regional Technical Specialist in the Hydraulics Section, Los Angeles District (SPL). He has over 30 years of professional experience in water resources engineering, specializing in river mechanics, sediment transport analysis and modeling, fluvial geomorphology, hydrology, storm water management and planning, and fishway and ecosystem restoration design. Dr. Eom has served as a Regional Technical Specialist for South Pacific Division (SPD) with emphasis on sediment and fluvial geomorphology since June, 2016. He provides technical support to all Districts within SPD for the projects related to sediment and scour, stream bank protection design, and geomorphic assessment. Also, he serves as a technical lead on multiple projects for SPL including hydraulic modeling and analysis, feasibility studies related to sediment removal, and ecosystem restoration. Dr. Eom earned a PhD degree from Colorado State University (Fort Collins, Colorado) in Hydraulic Engineering. He is a registered Professional Engineer (PE) in California.
Mr. Nicholas Olsen is a civil engineer in the Hydraulic Section pf the Los Angeles District, USACE. he has 5 years of experience in hydrologic and hydraulic modelling in addition to 3 years of field experience studying desert flash flooding and wetland biology.
Ms. Jackie Oehler is a civil engineer in the Hydrology & GIS Section of the Los Angels District, USACE. She has been with USACE for over 5 years and has worked on projects involving post-wildfire hydrology, watershed modeling, and ecosystem restoration. Ms. Oehler holds a B.S. in civil engineering from UCLA and is a registered professional engineer in the state of California.
Workshop Agenda:
Day 1: Tuesday, 9 September 2025
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
08:00 - 08:30 | 30 | Admin | Welcome, introductions Logistics, bathrooms, etc. | Jose Paredez | ||
08:30 - 09:30 | 60 | Overview of 2025 Wildfire Study | Discussions of methods, assumptions, and limitations: Hydrology (Curve Number/G&A), Sedimentation Yield, Reservoir Routing, and Hydraulics | Jose Paredez Moosub Eom Nicholas Olsen |
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09:30 - 09:45 | 15 | Break |
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09:45 - 10:30 | 45 | Lecture | Lecture 1: Overview of Hydrologic Modeling with HEC-HMS Discussion about model calibration, Frequency Storm and Hypothetical Storm development, and continuous simulation | Jose Paredez | ||
10:30 - 11:45 | 75 | Lecture | Lecture 2: Overview of Post-Wildfire Hydrology and Debris Flow Modeling Applications Discussion of the ways post-wildfire hydrology and debris yield modeling is used in studies including post-wildfire assessments, debris yield prediction, and post-wildfire flow risk and emergency management. | Jay Pak | ||
11:45 - 12:45 | 60 | Lunch |
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12:45 - 13:30 | 45 | Lecture | Lecture 3: Subbasin Debris Yield Analysis Introduction to five debris yield methods for debris yield assessment in burned mountain watershed. Discussion of appropriate use and parameter estimation. | Jay Pak | ||
13:30 - 14:30 | 60 | Workshop | Workshop 1: Quick Debris Yield Modeling based on Field Data Estimate the parameters for each debris yield method. Enter the initial parameter values within a basin model, create a simulation run, and compute the simulation. Calibrate and compare results to measured sample data. | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | ||
14:30 - 14:45 | 15 | Workshop Review |
| Jackie Oehler | ||
14:45 - 15:00 | 15 | Break |
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15:00 - 15:45 | 45 | Lecture | Lecture 4: Channel Sediment Routing in HEC-HMS Overview of channel sediment routing processes and methods in HEC-HMS. | Jay Pak | ||
15:45 - 16:45 | 60 | Lecture | Lecture 5: Debris Reservoir Routing Analysis Explanation of the physical reservoir volume reduction processes at reservoir. The reservoir sediment trap efficiency is affected by the detention time of storm runoff and by factors governing sediment particle size. | Jay Pak | ||
16:45 - 17:00 | 15 | Group Discussion |
| All |
Day 2: Wednesday, 10 September 2025
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
| 08:00 - 08:15 | 15 | Admin | Recap and Review | Jose Paredez |
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08:15 - 09:45 | 90 | Workshop | Workshop 2: Estimating Debris Yield in Debris Basin Practice calibrating debris yield modeling without/with Debris Reservoir/Basin and compare results with measured data. | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | Old Task 2: Debris Yield Modeling without Debris Basin (with New Debris Volume Conversion to Mass Unit Weight/Density) (Sediment Restructure: HMS 4.14) Optional: Old Task 3: Debris Yield Modeling with Debris Basin (with New Debris Volume Conversion to Mass with Unit Weight/Density) (Sediment Restructure: HMS 4.14) | |
09:45 - 10:00 | 15 | Workshop Review |
| Jackie Oehler | ||
10:00 – 10:15 | 15 | Break | ||||
10:15 - 11:00 | 45 | Lecture | Lecture 6: Post-Wildfire Hydrologic Analysis: Event & Continuous Models Explanation of a surface dynamic infiltration loss method to develop a long-term post-wildfire hydrologic model for a burned watershed. Discussion of the physical basis for the parameters and procedures for post-wildfire effect. | Jay Pak | ||
11:00 - 12:10 | 70 | Workshop | Workshop 3: Post-Wildfire Hydrology Analysis using Surface Dynamic Infiltration Loss Method: Use a surface dynamic infiltration loss method to estimate parameters for the long-term post-wildfire hydrology model. Practice calibrating model and compare results with observed flow (gage data). | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | ||
12:10 – 13:10 | 60 | Lunch | Lunch / Networking | |||
13:10 - 13:25 | 15 | Workshop Review |
| Jackie Oehler | ||
13:25 - 14:20 | 55 | Lecture | Lecture 7: Post-Wildfire Hydrologic Analysis: CN Loss Method and G&A Method Explanation of two principal approaches for estimating post-fire infiltration loss: The NRCS Curve-Number (CN) method and the Green-Ampt (G&A) method. | |||
14:20 – 15:05 | 45 | Lecture | Lecture 8: Model Calibration Optimizing hydrologic and sediment yield predictions: A calibration approach using historical precipitation and streamflow records. | Jackie Oehler | ||
15:05- 15:45 | 40 | Demo/Workshop | Demo 1: Calibration Calibrating hydrologic parameters using historical precipitation and streamflow records | Jackie Oehler | ||
15:45 - 16:00 | 15 | Break | ||||
16:00 – 16:30 | 30 | Lecture | Lecture 9: Outlet Tower Procedures for defining and Adjusting Outlet Tower geometry and operational parameters within the Reservoir Element. | Jackie Oehler | ||
16:30 – 16:45 | 15 | Demo | Demo 2: Intake Tower Bailey Outlet Tower | Jackie Oehler | ||
16:45 – 17:00 | 15 | Group Discussion | All |
Day 3: Thursday 11 September 2025
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
08:00 - 08:15 | 15 | Admin | Recap and Preview | Jose Paredez |
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08:15 – 08:45 | 30 | Demo | Demo 3: Calibration a reservoir element Calibrate debris-basin sediment yield and sediment-surface elevation using observed measurements | Jackie Oehler | ||
08:45 – 09:30 | 45 | Lecture | Lecture 10: Real-Time Simulation using Precipitation Forecast Implementing real-time flood forecasting with HEC-HMS: Procedures for data acquisition, model development, and simulation runs. | Jose Paredez | ||
09:30 – 10:00 | 30 | Demo | Demo 4: Real-Time Simulation using Precipitation Forecast Implementing real-time flood forecasting with HEC-HMS for Bailey Debris Basin. | Jose Paredez | ||
10:00 - 10:15 | 15 | Break | ||||
10:15 - 11:00 | 45 | Lecture | Lecture 11: Post-Wildfire Hydraulic Analysis Explanation of non-Newtonian flow models in HEC-RAS, which are used to account for internal losses affecting the md and debris flows. | Moosub Eom Nicholas Olsen | ||
11:00 – 12:30 | 90 | Demo | Demo 5: Debris flow modeling Debris flow inundation mapping application using the non-Newtonian models in HEC-RAS. | Moosub Eom Nicholas Olsen | ||
12:30 - 13:30 | 60 | Lunch | ||||
13:30 - 14:15 | 45 | After-Action Review |
| Jose Paredez | ||
14:15 - 17:00 | 165 | Knowledge Sharing | LA District Planner: DWR: CGS: LACDPW: | All |